If someone loses sight in an eye, or closes one eye, the brain can still interpret depth even though the binocular input has been lost. This is very different than what has happened to Marc. In his case, presumably, both eyes are functioning and the binocular signal is getting to the brain but cannot be interpreted. Other depth signals also can't be interpreted. That's why this may not be a case for a shhotgun coach - it isn't an "eye" or "dominant eye" problem.
Again, a neurologist with traumatic damage experience is the person to see.
